1. Field of the Invention
The present invention relates to an image offset adjustment apparatus for an Liquid Crystal Display (LCD) projector which is constructed to enable the adjustment of an image offset in an LCD projector.
2. Description of the Related Art
Projectors that can project a small image on a large screen and that use a flat display having a slim configuration, instead of a Cathode Ray Tube (CRT) display limited screen size and a large system size, has drawn considerable attention. While a projector can adopt a CRT or an LCD as a display for a small image, an LCD projector using an LCD has been highlighted in step with the trend toward miniaturization. An LCD projector employs a transmission type LCD or a reflection type LCD.
The LCD projector has been developed for miniaturized size, light weight and high brightness, and the LCD has been developed for high aperture ratio and high resolution. Therefore, in order to achieve high resolution, miniaturization and low cost which are demanded in the LCD projector, a reflection type LCD is generally preferred in use as a display.
The LCD projector represents a system in which light is transmitted to an LCD serving as an image generation module to generate an image and the generated image is projected to a large screen after being enlarged through optical lenses.
FIG. 1 illustrates the optical construction of an LCD projector 1. The LCD projector 1 comprises a light source 2 for generating light A1 and having a parabolic mirror (not shown), first and second reflection mirrors 3 and 4 arranged in front of the light source 2, an LCD 5 and a plurality of projection lenses 6 installed in front of the reflection mirrors 3 and 4. A screen 7 is placed in front of the projection lenses 6. Any flat surface can act as a screen.
The parabolic mirror (not shown) is disposed behind the light A1 and reflects the light A1 incident on the reflection surface thereof. The parallel light rays reflected from the parabolic mirror are incident on the LCD 5. As electric signals corresponding to an image to be obtained are selectively applied to a plurality of electrodes for driving liquid crystals, the alignment of the liquid crystals filled in the selected electrodes is changed, and an image 8 is generated. The image 8 generated in the LCD 5 is enlarged by the projection lenses 6, and the enlarged image 8 is projected on the screen 7. The first and second reflection mirrors 3 and 4 function to reflect an optical path so that the locations of the respective component elements are suited to the size and the configuration of the system.
In the LCD projector 1, in order to ensure that a clear image is obtained on the screen 7, the respective component elements including the projection lenses 6 are optically arranged in a manner such that the image 8 which is generated by selectively transmitting the light A1 incident on the LCD 5 can be precisely focused on the screen 7.
As shown in FIGS. 2 and 3, the entire area measured between the projection lenses 6 and the lower and upper ends of the image 8 is referred to as the image offset of the LCD projector.
As shown in FIG. 2, when projecting the image 8 on the screen 7, the image offset indicates the entire image. When the projected image is referenced as 100%, and if a projection angle is changed to accomplish an image offset greater than 100%, the changed projection angle remains fixed. This is because it is impossible to change a projection angle once the projection angle is set.
In the conventional LCD projector, since an image offset value is set in conformity with the fixed position of the projection screen, in the event that the size and position of the image are altered, the image offset cannot be adjusted in conformity with the altered size and position of the image, whereby a clear image cannot be provided.
Also, in the case where an image offset adjustment apparatus is separately mounted to the conventional LCD projector, the size of the resultant LCD projector is increased, which affects the miniaturization of the LCD projector.
Miniaturized LCD projectors are now being supplied in mobile phones.
A mobile phone provides a communication function and various additional service functions. That is, in addition to a wireless communication function, the mobile phone provides a variety of functions for processing multimedia data. The mobile phone capable of processing multimedia data can include a camera, a TV receiver, a satellite broadcasting receiver, programs for performing various functions such as games, and so forth. Therefore, the mobile phone has been developed as a multi-functional terminal.
Each of the various functions is implemented in a manner such that the image of the corresponding function is displayed on the display screen of the mobile phone and an audio is provided along with the image. For example, as a user selects broadcasting among TV channels through a conventional mobile phone, an image of the selected TV channel is provided on the display screen of the mobile phone, and audio is provided through a speaker built in the mobile phone or an earphone connected to the mobile phone.
The conventional mobile phone has a problem in that, since the size of a display screen for displaying an image is limited, the image generated in the mobile phone cannot but be provided to the user only through the limited display screen of the mobile phone. In order to cope with this, problem, the LCD projector can be provided to the mobile phone to enable display of an enlarged image.
However, in this case, because the mobile phone having the conventional LCD projector requires a separate screen which must be always carried together with the mobile phone, the portability of the mobile phone is deteriorated. Also, when the mobile phone is used for various documents or personal entertainment, due to the fixed projection angle of the LCD projector, the size and the position of a desired projection screen vary depending upon the size of an image to be projected, whereby it is impossible to provide a clear image. In order to provide a clear image, while the image offset of the LCD projector must be adjusted, a separate image offset adjustment apparatus is not provided to the LCD projector.